Defines dateType for the form

<div class="definition">
    String, default = null
</div>

If dataType is not defined, the default one comes from
<a href="w2utils.settings" class="method">w2utils.settings.dataType</a>.
<div style="height: 10px"></div>

This property can be set during object creation:
<textarea class="javascript">
let form = new w2form({
    name: 'form',
    dataType: 'JSON',
    url: '/server/url',
    fields: [
        { field: 'first_name', type: 'text', required: true },
        { field: 'last_name', type: 'text', required: true },
        { field: 'email', type: 'email' }
    ],
    actions: {
        "save": function () { this.validate(); },
        "reset": function () { this.clear(); }
    },
})
</textarea>

Or any time during run-time:
<textarea class="javascript">
form.dataType = 'JSON';
</textarea>
